Searching for sliding surfaces in multi-level loess slopes based on the brachistochrone.

As a key problem in slope-stability analysis, searching for potential sliding surfaces has attracted the attention of experts and scholars for a long time. However, the commonly used sliding surface curves are only considered in terms of shape approximation and lack physical significance. The search process involved in stability analysis of multi-level slopes is complex and a large amount of calculation is required. In order to solve this problem, this paper proposes a new sliding surface form based on physical interpretation of the brachistochrone, and establishes a search model for the brachistochrone sliding surface of a multi-level loess slope. At the same time, in order to further expand the search range and find a more ideal potential sliding surface curve shape and position with a lower safety factor, we recommend continuing the sliding-surface search after the brachistochrone is improved. We compared the calculation results for the position of the potential sliding surface and the stability safety factor with the corresponding results for an arc sliding surface (in combination with a calculation example) to verify its rationality. The approach offered here not only provides a new choice of sliding surface curve form for slope-stability analysis, but also significantly improves search efficiency for potential sliding surfaces of multi-level loess slopes.

[Factors of effects on transformation behaviors of inorganic mineral matters in desulfurizing process of burning coal].

The Heshan coal and the Wansheng coal were selected to investigate the effects of Ca/S molar ratio, combustion temperature and other factors on the desulfurization efficiency when limestone as a desulfurizer. And then the possible effects of various desufurizing systems on the mineral constituents of their residues were discussed by using the X-ray diffraction analyzer. Moreover, the phase diagrams of the ternary system CaO-Al2O3-SiO2 were further used in order to find out the transformation behaviors of inorganic mineral matters in the desulfurizing processes of burning coal on the basis of the XRD results. The results show that the combustion temperature and the Ca/S molar ratio are the key factors affected the desulfurization efficiency and their residues' mineral constituents. When the temperature raised and the Ca/S ratio increased, the solid-phase reactions between CaO and some inorganic matters in coal ash will be obviously accelerated, which thus are good for the formaion of many mineral matters such as C4AF,C2AS and beta-C2S. Yet the anhydrite formed will decompose if the temperature is above 1050 degrees C and then the desulfurization efficiency will decrease. The desulfurization efficiency in different temperature is mainly decided by the existence form of the sulfur-contained mineral matters and their contents in the residue. In the experiment, the best desulfurization efficiency for the HS coal was about 90% when the Ca/S ratio was 2 or 3 and the range of the temperature was from 850 degrees C to 950 degrees C.